中空纳米二氧化硅微球的制备及表征

本文介绍了一种制备中空纳米二氧化硅微球的新方法。利用模板首先合成介孔纳米二氧化硅微球,再用水热反应法,成功制备了非功能化和巯基、氨基功能化中空纳米二氧化硅微球。利用透射电子显微镜,热重分析等手段对其形貌进行了表征。另外,对中空介孔纳米二氧化硅微球的形成机制进行了探讨。     

Robust Amino-Functionalized Mesoporous Silica Hollow Spheres Templated by CO2 Bubbles

Hollow-structured mesoporous silica has wide applications in catalysis and drug delivery due to its high surface area, large hollow space, and short diffusion mesochannels. However, the synthesis of hollow structures usually requires sacrificial templates, leading to increased production costs and environmental problems. Here, for the first time, amino-functionalized mesoporous silica hollow spheres were synthesized by using CO₂ gaseous bubbles as templates. The assembly of anionic surfactants, co-structure directing agents, and inorganic silica precursors around CO₂ bubbles formed the mesoporous silica shells. The hollow silica spheres, 200–400 nm in size with 20–30 nm spherical shell thickness, had abundant amine groups on the surface of the mesopores, indicating excellent applications for CO₂ capture, Knoevenagel condensation reaction, and the controlled release of Drugs.     

Gemini Surfactants Templated Mesoporous Silica Microparticles: from Solid to Hollow Mesoporous Spheres

We synthesized a series of mesoporous silica microparticles (MSs) using cationic gemini surfactants C_14–2‐n (n = 2, 6, 10, 14) as templates. The porous structures and pore size of these MSs can be tuned by varying the length of alkyl chain in gemini surfactant templates. These MSs showed effective doxorubicin (DOX) loading and a pH‐responsive drug release characteristics. These results indicate that the MSs, especially the hollow mesoporous silica nanoparticles, have great potential for biomedical applications.     

Fabrication of Mesoporous SiO2@CaSiO3 Hollow Spheres as Carriers for pH-sensitive Drug Delivery

Hollow mesoporous silica(HM-SiO₂) was prepared by the improved stober method. On this basis, HM-SiO₂ was dispersed in an alkaline solution for surface etching. Meanwhile, calcium source was introduced to combine with on the surface to form a CaSiO₃shell layer and an unprecedent SiO₂@CaSiO₃sphere with a hollow double-shell structure was obtained. The as-synthesized SiO₂@CaSiO₃ was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), N₂-BET, IR and UV-Vis techniques, and its sustained release capacity of doxorubicin(DOX) loading was investigated. The drug loading capacity can be achieved to 0.692 mg DOX/mg SiO₂@CaSiO₃, exhibiting pH-responsivity under low pH conditions.     

Rapid Fabrication of Hollow SiO2 Spheres with Novel Morphology

The hydrolysis of tetraethoxysilane (TEOS) occurred on the surface of poly(methyl methacrylate) (PMMA) microshperes immediately after these microshperes were prepared in TEOS. Micron-sized hollow SiO2 spheres were obtained by calcination of the coated PMMA microshperes. It was found that the final hollow spheres were constituted by small SiO2 particles.     

空心玻璃微珠/TiO2复合微球的制备及其性能研究

本文以脲为沉淀剂,通过化学沉淀法成功实现了锐钛矿型二氧化钛壳层在空心玻璃微珠表面的可控组装,从而制备出玻璃/二氧化钛核壳空心微球,并通过XRD、SEM、EDX和拉曼光谱对其结构、形貌、粒径、壳厚和化学组成进行了表征.提出了二氧化钛在空心玻璃微珠表面的定向生长的可能机制和形成过程.     

一种制备单分散SiO2空心微球的新方法

在乙醇/氨水介质中, 分别以分散聚合和无皂乳液聚合方法制得的不同粒径聚苯乙烯(PS)微球为模板, 以正硅酸乙酯(TEOS)为前驱体, 通过控制介质中氨水的初始体积, 一步法制得了不同粒径的单分散SiO2空心微球. 整个过程无需添加其它溶剂溶解或高温煅烧的方法来除去模板微球. 对SiO2空心微球进行测试表征, 提出了SiO2空心微球的可能形成机制.     

利用具有核壳结构的SiO2@PPy粒子制备SiC空心球

碳化硅(SiC)材料具有耐高温、 耐酸碱腐蚀和高机械强度等优异性能, 因此, 许多研究者都致力于制备优良的SiC材料以取代传统材料用作苛刻条件下催化剂的载体材料[1～4]. 研究结果表明, 具有高比表面积和空心核结构的载体材料可以负载更多的异质催化剂, 从而提高催化剂的催化性能. 因此, 制备同时具有高比表面积和空心核结构的SiC材料具有重要的应用价值. 传统的碳热还原反应、 自蔓延高温合成、 聚合物热分解等方法都不适合制备具有独特结构形貌的SiC材料[5～8]. 近年来, Ledoux等[1～4, 9]采用形状记忆合成(Shape memory synthesis)方法将不同形貌的固相碳材料与气相SiO蒸气反应, 成功地制备了不同形状的SiC材料, 比表面积在20～100 m2/g之间. Vix-Guterl等[10- 11]采用反应复制技术(Reactive replica technique)从C/SiO2材料制备了微米级的管状SiC材料. 另外, Tang等[12]采用水热合成法得到了纳米级的SiC空心球, 但产率不高. 本文利用具有核壳结构的SiO2@PPy粒子在1 300 ℃进行碳热还原反应, 成功制备同时具有较高比表面积和空心核结构的SiC空心球材料.     

MoO2微米空心球的水热合成及合成机理研究

Micrometer-sized MoO2 hollow spheres were synthesized hydrothermally with ammonium heptamolybdate tetrahydrate as molybdenum source, Cetyltrimethylammonium bromide as structure-directing agent and C2H5OH as reducing agent, respectively. The products were investigated by X-ray diffraction, thermo- gravimetry and differential thermal analysis, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A morphology transition of "blocks-solid spheres-hollow spheres" during the growth process was observed and the possible mechanism for the formation of MoO2 samples was proposed to be through a microscale Kirkendall effect.     

Poly(St-co-DMC)/SiO_2杂化及空心杂化纳米粒子的合成及表征

采用无皂乳液聚合法合成了聚(苯乙烯-co-甲基丙烯酰氧乙基三甲基氯化铵)(poly(St-co-DMC))纳米粒子,平均粒径约为100 nm.以此纳米粒子为模板,在接近室温及p H为中性的温和条件下,以四甲氧基硅烷(TMOS)为硅源,合成了poly(St-co-DMC)/Si O2杂化纳米粒子,TEM结果显示该纳米粒子具有明显的核壳结构,Si O2主要沉积在壳层.进一步通过四氢呋喃溶解制备得到具有空心结构的纳米粒子,这种空心结构纳米粒子的FTIR图谱中既有Si O2的信号,也有poly(St-co-DMC)的信号,说明空心纳米粒子的壳层不完全是Si O2,对空心纳米粒子的TGA结果分析计算得到Si O2的含量仅为69.7%,说明纳米粒子的壳层为杂化壳层,并且,这种壳层的厚度随着反应温度的升高、反应时间的延长、TMOS用量的增加及聚合物模板中DMC含量的增加而增大.     

氨水诱导硅核自组装制备介孔SiO_2

在无模板剂的条件下,通过控制氨水用量,利用正硅酸乙酯水解制备了粒径约20 nm的SiO2初级粒子;随后用过量氨水诱导SiO2初级粒子交联生长,得到孔径在10~50 nm、孔容达2.05 cm3.g-1的介孔SiO2;考察了介孔SiO2的吸附性能.结果表明,所制备的介孔SiO2具有优良的吸附性能.     

Formation of Triple‐Shelled Molybdenum–Polydopamine Hollow Spheres and Their Conversion into MoO2/Carbon Composite Hollow Spheres for Lithium‐Ion Batteries

Unique triple‐shelled Mo‐polydopamine (Mo‐PDA) hollow spheres are synthesized through a facile solvothermal process. A sequential self‐templating mechanism for the multi‐shell formation is proposed, and the number of shells can be adjusted by tuning the size of the Mo‐glycerate templates. These triple‐shelled Mo‐PDA hollow spheres can be converted to triple‐shelled MoO₂/carbon composite hollow spheres by thermal treatment. Owing to the unique multi‐shells and hollow interior, the as‐prepared MoO₂/carbon composite hollow spheres exhibit appealing performance as an anode material for lithium‐ion batteries, delivering a high capacity of ca. 580 mAh g^?1 at 0.5 A g^?1 with good rate capability and long cycle life.     

新型HPW/SiO2复合介孔材料的合成与表征

合成了一种新型的HPW/SiO2复合介孔材料,通过XRD,TEM,UV-Vis和FTIR等表征证明,HPW均匀且稳定地包藏到介孔材料由SiO2网络组成的孔壁之中.催化结果表明,其在大分子催化反应中有较高的活性,在酯化反应中连续循环使用未发现活性组分流失,表明其在多相催化和大分子催化反应中有较好的工业应用前景.     

介孔SiO_2球为模板制备TiO_2纳米纤维及光催化合成氨

以介孔SiO_2球为模板,TiCl_4为前躯体,制备了高催化活性的TiO_2纳米纤维以及非晶态合金(Ni-Mo-B)修饰的纳米纤维.TiO_2纳米纤维直径为7~10 nm,结晶度高,不仅对紫外光有很强的吸光度,而且对可见光也有一定程度的吸收.此外,纳米纤维降低了荧光强度,稳定了光生电子-空穴对.经过非晶态合金(Ni-Mo-B)修饰的纳米纤维进一步降低了荧光强度.在紫外光催化N_2与水合成氨的反应中,当反应时间为2 h时,P25氨氮产量为31μmol,Ti的转换频率(TOF)为0.5·h-1.纯TiO_2纳米纤维氨氮产量提高了约71%,达53μmol,Ti的转换频率(TOF)提高到了0.8·h-1.经过非晶态合金修饰的纳米纤维,氨氮产量达66μmol,Ti的转换频率(TOF)为0.95·h~(-1),比P25提高了113%.     

电解质诱导聚集初级粒子制备介孔SiO_2材料

在无模板剂的条件下,通过在Stber合成过程中引入外加电解质成功地制备了具有介孔结构的SiO2粒子.实验结果表明,通过电解质的加入可以诱导Stber过程中初级SiO2粒子的聚集,从而得到了具有介孔结构和较强表面吸附能力的SiO2粒子.     

CMC和CTAB双模板法合成具有稳定结构的MCM-41中孔分子筛

以羧甲基纤维素和十六烷基三甲基溴化铵为双模板,制备出了具有更高稳定性并且具有高度有序二维六方结构的MCM-41介孔分子筛.透射电镜和X射线衍射结果表明,以双模板制备的MCM-41介孔分子筛具有高度有序的二维六方(p6mm)孔道结构.此外,以双模板制备的MCM-41介孔分子筛焙烧前后的X射线衍射结果表明,在焙烧过程中其晶胞收缩比例为3.1%.与以纯表面活性剂为模版制备的MCM-41介孔分子筛(晶胞收缩比例为9.7%)相比,双模板制备的MCM-41介孔分子筛具有更高的稳定性能. MCM-41介孔分子筛稳定性能的提高可能是由于在硅物种、表面活性剂以及羧甲基纤维素在自组装过程中,羧甲基纤维素表面丰富的羟基与硅物种Si-(OH)x的相互作用促进了Si-(OH)x的缩聚.     

Facile H2O2 Hydrothermal Synthesis of Bimodal Mesoporous Silica MCM-48 Spheres

The ordered bimodal mesoporous silica MCM-48 spheres were facile synthesized by mild-temperature post-synthesis H₂O₂ hydrothermal treatment of as-synthesized MCM-48. The results showed that H₂O₂ is indispensable for simultaneously removing organic templates and forming ordered bimodal mesoporous silica MCM-48 spheres. The bimodal mesoporous MCM-48 was characterized by X-ray diffraction, transmission electron micrographs, FT-IR, and N₂ adsorption-desorption, and a possible mechanism was proposed for the formation of bimodal mesoporous MCM-48.     

Ethylene Adsorption and Oxidation Kinetics in the Reactions with Pd(II)/SiO2 and Cr(VI)/SiO2: Consideration of Substrate Distribution between the Gas Phase,Silica Gel,and Reaction Centers

The kinetics of ethylene oxidation by PdCl₂ and CrO₃ complexes supported on silica gel (300 K, closed batch reactor) and the adsorption of C₂H₄ by silica gel and metal complex reaction centers (M ⁿ ) were studied. A new version of the kinetic distribution method was applied to determine the rate constants of ethylene reactions with metal complexes with consideration for the equilibrium distribution of C₂H₄ among the reactor gas phase, silica gel, and M ⁿ . The rate constant of a first-order reaction with respect to Cr(VI) (k _e) remained constant as [M ⁿ ] was increased up to 0.15 mol % with the absence of detectable ethylene adsorption by chromium(VI). In the case of Pd(II)/SiO₂, strong ethylene adsorption by palladium(II) was found, and k _e was an exponential function of [M ⁿ ]. This exponential function is indicative of an increase in the specific activity of Pd(II) with palladium concentration on SiO₂. Taking into account the adsorption of ethylene (physisorption on SiO₂ and chemisorption on Pd(II)), we found an analogy between the kinetic behaviors of Pd(II) in reactions with ethylene on silica gel and with ethylene and other hydrocarbons in solutions.     

Nd(III) and Gd(III) Sorption on Mesoporous Amine-Functionalized Polymer/SiO2 Composite

The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g⁻¹ and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g⁻¹ and 1 mmol Gd g⁻¹. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30–40 min). At pH close to 4–5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity.